Battery or alternator

hi i have a 98 monte carlo and it started with my voltage light coming on. so i took it to auto zone and had the battery tested and the alternator. they said they seemed to think it was the connection wires so after cleaning those it was just fine. the amps read the same coming and going from the battery and alternator. but when i went back out to start it again i started having the same problem. even purchased a new battery and that didnt fix it... one time it works fine and then the next the light comes back on and my inside light will dim along with my head lights when the car is given gas... any suggestions on what to do now????

thanks alot

check wires and cables again. this time check ground wire to engine block. also make sure all are tight. also battery cables can corrode inside and look fine outside the insulation. if all wires and cables check ok, then have diodes in alternator tested. good luck !

hi i have a 98 monte carlo and it started with my voltage light coming on. so i took it to auto zone and had the battery tested and the alternator. they said they seemed to think it was the connection wires so after cleaning those it was just fine. the amps read the same coming and going from the battery and alternator. but when i went back out to start it again i started having the same problem. even purchased a new battery and that didnt fix it... one time it works fine and then the next the light comes back on and my inside light will dim along with my head lights when the car is given gas... any suggestions on what to do now????

thanks alot

the alternator has a regulator built into it. this component over time corrodes. this will cause voltage/current output to vary.

since the battery was load tested as good, the wire/connections removed cleaned and reinstalled I would check the voltage coming out to the battery terminals. then check the voltage at the alternator red wire make sure it is 14-15 volts dc. if you get less than 13.5volts there is an alternator problem.

DO THIS TEST WILL ALL LIGHTS ON AND AC/BLOWER AT MAX..

The other cause would be a belt issue. idlers/belts damaged/wrong size/contaminated. could also be a ac compressor pulley bearing locking up sometimes.

the alternator can be removed and brought to autozone for a bench testing. this will reveal if its defective.